Invoke like `hspresent pathtoyourpresentation`. Left and right arrow keys
move between slides, and hitting q or Ctrl-C quits the presentation.

The file format is really simple right now. Slides are separated by lines
consisting of the characters --. You can put the single character . on a
line to demarcate a split frame. A split frame really creates a new frame with
the contents of the previous frame copied at the front (this is similar to how
beamer works).